Friday Field Photo #136: Ripple Cross-Laminated Sandstone

This week’s Friday Field Photo is from Permian strata (~250 million years old) exposed in the Karoo desert of South Africa. This is a pretty nice example of a sedimentary structure you might hear referred to as a ‘starved ripple’. Note the foresets on the ripples dipping from left to right in the lighter-colored sandstone in middle of photo (just below the pencil). The view above is in cross section — check out these great photos from Callan Bentley showing ancient ripple marks on the bedding plane.

You want more explanation of how ripple cross-lamination forms? Of course you do. Check out this video explanation.